A stash of bug bombs apparently caught fire and exploded in the basement of a Chinatown building Thursday, injuring eight people in the business and apartments above, NBC 4 New York has learned.

An official familiar with the investigation said the bug foggers, which are used by exterminators to release pesticides, were stored in the basement of the five-story building on Pike Street. It's not clear how they caught fire, but one official said a faulty gas line was being examined.

Three of the injuries were described as serious and five were not life-threatening. Firefighters broke windows in an alley to reach people and pull them to safety as their loved ones cried out from the street.

FDNY said there was also a partial collapse of the rear first floor, which is shared by a bus company and a beauty parlor.

The people most seriously injured were in homes on the second and third floors. The Red Cross said more than 40 people were displaced by the fire, including seven children.